This section provides background information related to the present disclosure which is not necessarily prior art.
Vehicles, such as automobiles for example, are typically equipped with suspension assemblies. Such suspension assemblies are positioned between a mounting location that is disposed on the vehicle and a wheel end assembly. The mounting location is typically disposed on either a body or frame of the vehicle, depending on how the vehicle is constructed. For example, the mounting location may be disposed on the frame where traditional body-on-frame construction is used, while the mounting location may be disposed on the body of the vehicle itself where frameless construction is used. The wheel end assembly supports one or more wheels of the vehicle and may include other vehicle components such as axels, differentials, hub assemblies, and brakes. The suspension assembly allows the wheel end assembly to move relative to the mounting location such that the wheels can move relative to the body and/or frame of the vehicle. As such, the suspension assembly generally improves the road holding, handling, and ride comfort of the vehicle.
One type of suspension assembly utilizes a longitudinal arm that extends between the mounting location and the wheel end assembly. Where this configuration is used at the front of the vehicle, such suspension assemblies are commonly referred to as leading arm suspension assemblies because the wheel end assembly is in front of the mounting location. Where this configuration is used at the rear of the vehicle, such suspension assemblies are commonly referred to as trailing arm suspension assemblies because the wheel end assembly is behind the mounting location. The longitudinal arm typically has a first end that is pivotally coupled to the mounting location and a second end that is pivotally coupled to the wheel end assembly. One or more shock absorbers and one or more suspension springs are installed between the body and/or frame of the vehicle and either the longitudinal arm or the wheel end assembly. The suspension springs bias the wheel end assembly toward an extended position where the wheel end assembly is spaced from the body of the vehicle and the shock absorbers provide a dampening force that opposes the movement of the wheel end assembly to prevent excessive oscillations in the suspension assembly.
A single bushing assembly is typically used to couple the longitudinal arm to the mounting location. An example of this conventional single bushing arrangement is described in U.S. Pat. No. 7,207,583, which issued to Ross et al. on Apr. 24, 2007. The longitudinal arm includes a mounting tube at the first end that receives a cylindrical bushing. A hanger is mounted on the frame and a bolt extends through both the hanger and the center of the cylindrical bushing to pivotally couple the first end of the longitudinal arm to the frame. The bolt therefore defines an axis of rotation for the longitudinal arm and the bushing is made of a compliant material such that the longitudinal arm can move in the vertical and longitudinal directions relative to the hanger to a limited extent due to the compliance of the bushing. This movement in the vertical (up and down) and longitudinal (fore and aft) directions, which can be expressed in terms of travel distance and rate, improves ride quality in comparison to a hard, bushingless pivot. The travel distance and the rate of the bushing are material specific parameters and are therefore interrelated. These parameters can be tuned somewhat by using complex bushing geometries where voids or other features of various shapes are formed in the bushing such that the bushing behaves differently in the vertical direction relative to in the longitudinal direction. More specifically, complex bushing geometries can be used to provide different travel distances in the vertical direction versus in the longitudinal direction and different bushing spring rates in the vertical direction versus the longitudinal direction. However, the material of the bushing limits how great the travel distance differential and the rate differential can be and complex bushing geometries typically increase the cost and decrease the durability of the bushing.